Cutting fluids are used in many metal cutting operations, as well as in grinding, to maintain optimum production rates, minimize tool wear, and improve surface finish, etc. One of the primary types of cutting fluids comprises emulsified oils which provide excellent cooling and lubrication for metal cutting at high speeds due to their high specific heat, high thermal conductivity, and high heat of vaporization. These cutting oils, as well as other oils from the metal working and handling machinery, remain on the workpart after manufacture and must be removed prior to use or sale of the workpart.
Various types of cleaning apparatus have been proposed in the prior art, such as dunk tanks and spray booths, all generally referred to as parts washers. In a parts washer, the cleaning fluid is used to wash the workpart free from surface born soils, such as oils and other hydrophobic, hydrocarbon fluids, as well as particulates. This cleaning fluid typically comprises a water base with various hydrophilic water soluble additives such as soaps, surfactants, defoamers and rust inhibitors, etc. These additives to the water base constitute the expensive ingredients, as well as those ingredients which are least readily degradable in the environment.
According to the prior art, as the oil and other hydrophobic fluids emulsified in the cleaning fluid become increasingly concentrated in the cleaning fluid, the cleaning fluid becomes less effective and is eventually discarded. Discarding dirty cleaning fluid is expensive due to the high cost of the cleaning additives, and also raises concerns of discharging the old oil and cleaning fluid into the environment. In some instances, special disposal arrangements are required for the old, used cleaning fluid.